In a bowl add raisins and hot water then set aside (no need to do this if you are using chocolate chips)
In another bowl, beat the butter until smooth and creamy
Slowly add the brown sugar while beating the butter
After, add the egg and vanilla to the bowl and mix it (not using the electric mixer)
Next, add the dry ingredients: flour, baking powder, salt, cinnamon, oats, cornstarch into the bowl (you might want to mix it using your hands as the mixture/cookie though will be thick)
If you are using raisins then drain the raisins then add them into the bowl (if you are using chocolate chips then add them into the bowl)
Scoop out balls of cookie dough, place them on the baking sheet, flatten the cookie dough ball
Bake them in 177C or 350F for 14 minutes or until golden
Let them cool and enjoy the oatmeal cookies